Halve the fingerling potatoes (if some are especially small, you can leave them whole; you want them all to be about the same size in order to roast evenly).

In a large bowl, toss the potatoes with olive oil, balsamic vinegar, thyme, salt and pepper. Spread the potatoes onto a rimmed baking sheet. Roast 30-40 minutes until cooked through and crispy on the outside, stirring occasionally.